Individuals with severe mental illness are at increased risk for weight gain due to side effects from atypical antipsychotics and mood stabilizers, sedentary lifestyle, and social isolation. Obesity is a known risk factor for developing depression and their bidirectional relationship warrants simultaneous treatment. This study looked at the relationship between clinical outcomes and change in BMI. In 2018, individuals (N=305) at a residential and outpatient adult rehabilitation program for major depression (49.5%), bipolar disorder (19.0%), anxiety (12.1%) and schizophrenia (10.5%) were studied. Pre and post treatment outcomes were collected on hope (BHS), medication attitudes (MAI), functional gains (BASIS-32) and depression symptoms (MADRS). The treatment program implements evidence-based pharmacological interventions, psychotherapy, social/vocational training and a wellness intervention (personal training, meal plan, psychoeducation). Regular monitoring of physiologic indices and medication treatment was provided as indicated. Paired outcomes were collected for 216 patients with diagnoses, gender and age distribution similar to the treatment population. Overall, the patients experienced a statistically significant BMI increase (mean=1.52, p=0.00). Male patients experienced a higher rate of BMI gains than females. Individuals with bipolar depression had the largest average BMI increase (mean=1.86, p=0.00). Patients with BMI decreases had 25% greater improvement in hopefulness (mean BHS=4.86, p=0.00) than patients that gained weight (mean BHS=3.59, p=0.00). Patient medication attitude improved (mean MAI=3.12, p=0.00) 40% more than those that increased BMI (mean MAI=2.19 p=0.00). Finally patients that lost weight had a 25% greater reduction in depression symptoms (mean MADRS=13.97, p=0.00) than those that gained (mean MADRS=10.44, p=0.00).